Acrylic fibers and process for preparing the fibers

ABSTRACT

TEXTILE FIBERS OF SYNTHETIC ACRYLONITRILE POLYMER HAVING DISPERSED THROUGHOUT THE CROSS SECTION OF THE FIBER A SALT OF A PARTIAL ESTER OF PHOSPHORIC ACID WITH A MONOALKYL ETHER OF A POLYOXYALKYLENE GLYCOL; SAID SALT BEING PRESENT IN THE AMOUNT OF ABOUT 0.05% TO ABOUT 3% BY WEIGHT OF THE POLYMER TO REDUCE WASTE IN FOBER PROCESSING OPERATIONS AND TO PROVIDE A YARN OF THE FIBERS HAVING IMPROVED QUALITY. ALSO, THE PROCESS FOR PREPARING THE ABOVE FIBERS.

Nov. 9, 1971 M. JONKOFF 3,618,307

ACRYLIC FIBERS AND PROCESS FOR PREPARING THE FIBERS Filed Nov. 14, 1968 FIG. I

I I o I 0 INVENTOR IMRE M. JONKOFF BY g/W ATTOR NFIY United States Patent Ofice 3,618,307 Patented Nov. 9, 1971 3,618,307 ACRYLIC FIBERS AND PROCESS FOR PREPARING THE FIBERS Imre M. Jonkolr, Camden, S.C., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. Filed Nov. 14, 1968, Ser. No. 775,794

Int. Cl. C08f 3/76; C10m 1/44; D02g 3/02 US. Cl. 57-140 R 14 Claims ABSTRACT OF THE DISCLOSURE Textile fibers of synthetic acrylonitrile polymer having dispersed throughout the cross section of thefiber a salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol; said salt being present in the amount of about 0.05% to about 3% by weight of the polymer to reduce waste in fiber processing operations and to provide a yarn of the fibers having improved quality. Also, the process for preparing the above fibers.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to an improved acrylic fiber that resists mechanical degradation and forms very little waste when stretch-broken as a multifilamentary tow to form staple sliver and subsequently processed to staple yarn. The invention relates also to a novel process for preparing the improved fibers.

(2) Description of the prior art In the production of acrylic staple yarns, one widely used commercial method involves conversion of a multifilamentary tow to a staple sliver by a stretch-breaking process on apparatus such as that described by Wyatt in US. Pat. 2,748,426. In this process, the acrylic filaments are stretched between feed nip rolls and delivery nip rolls while being struck by breaker bars positioned between the pairs of rolls. The breaker bars increase the tension upon the filaments in the tow sheet, inflicting stress concentration points upon the filaments to break them progressively to staple fiber length without destroying the continuity of the resulting sliver. The sliver so produced is then processed to conventional staple yarns by known methods, such as by spinning on the worsted system.

A significant problem in the commercial preparation of sliver from multifilamentary tows employing stretchbreaking apparatus incorporating breaker bars is that mechanical degradation of the fibers occurs during the process, with formation of airborne waste, known as fly, which consists mainly of short fibers. Approximately 80% of the fly consists of fibers less than two inches in length. This waste material becomes detached from the sliver during its preparation on the stretch-breaking apparatus, resulting in reduced yield of theproduct. Not only does this result in economic loss in proportion to the amount of fly which is formed, but also the accumulation of the fly on the equipment and in adjacent areas creates a cleaning and equipment maintenance problem. Also, it is found that only a part of the short fiber waste material drops out during the manufacture of the staple sliver on the stretch-breaking apparatus. Additional quantities of the waste material become detached at each stage of the conversion of the staple sliver to the staple yarn, resulting in additional cleaning and maintenance problems and reduced yield at each stage. In roving and spinning, fly waste picked up by the thread-line causes breaks, resulting in loss of spindle operation time, and quality defects in the yarn. Slubs of wound-in waste in the yarn frequently cause needle breaks, resulting in fabric defects.

SUMMARY OF THE INVENTION The present invention provides an improved acrylic fiber which, in the form of a multifilamentary tow, undergoes relatively little mechanical degradation to waste in the form of short fibers when stretch-broken to staple fiber and processed to staple yarn. Another advantage is to provide a novel process for preparing the improved acrylic fiber.

In accordance with the invention, a fiber is provided comprised of an acrylonitrile polymer and containing throughout the cross section of the fiber, a salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol; said salt being present in the amount of 0.05 to 3.0%, based on the weight of the polymer.

Surprisingly, up to 70% lower waste is encountered in the stretch-breaking of multifilamentary tows of the acrylic fiber of the invention, as contrasted with conventional acrylic fibers which do not contain the salt of a partial ester of phosphoric acid. Greatly reduced waste in subsequent processing steps is similarly observed. Yarns made from the fiber of the invention also exhibit improved uniformity, with respect to yarns made from conventional acrylic fibers.

The invention also provides a novel process for preparing the improved fibers, in which a salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol is dispersed in a solution of an acrylonitrile polymer to form a homogeneous spinning solution, and the spinning solution is then extruded through orifices of a spinneret to form fibers.

The product of this invention in its narrower scope is defined as textile fibers of synthetic acrylonitrile polymer having dispersed throughout the cross section of the fiber a salt of a partial ester of phosphoric acid with a mono alkyl ether of a polyoxyalkylene glycol; said salt being present in the amount of about 0.05 to about 3% by weight of the polymer to reduce waste in fiber processing operations and to provide a yarn of the fibers having improved quality. Included within the scope are the embodiments wherein: a paraffin wax is dispersed as an extender throughout the cross section of the fiber along with the salt; the salt is a sodium salt of a lauryloxypoly(ethylene oxy) acid phosphate of the formula i 12 25 2 1120) x]n P (ONa)3- wherein n is 1 or 2 and x is about 4; the salt is in the form of rod-like globules with the longitudinal axes of the globules extending in the direction of the fiber length; and staple yarns of said fibers.

The process of the present invention is more specifically described as being in the production of synthetic fibers of acrylic polymer in which the polymer is dissolved in a solvent to provide a spinning solution and the resulting solution is extruded in a spinning zone to form filaments which are subsequently processed to produce acrylic fibers; the improvement which comprises including in said spinning solution a salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol, said salt being present in said solution in the amount of about 0.05% to about 3% by weight of the polymer to provide a dispersion of the salt throughout the cross section of the filaments.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better undestood by reference to the attached figures, which illustrate sections of the fiber of the present invention.

FIG. 1 is an interior portion of a greatly magnified cross section of the fiber of the present invention containing a salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol; and

FIG. 2 is a greatly magnified longitudinal section of the fiber of the present invention, along its axis.

In FIG. 1, a portion of the interior of a cross section of the fiber of the invention, perpendicular to its axis, is seen. In this cross section, globules 1 of substantially round cross section of the salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol are seen together with particles 2 of TiO delusterant of irregular cross section embedded within the matrix of acrylonitrile polymer 3.

In FIG. 2, a segment of a longitudinal section of the fiber, substantially along its axis, is shown. In this longitudinal section, rod-like streaks 4 of the salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol are seen together with particles 2 of TiO of irregular cross section embedded within the matrix of acrylonitrile polymer 3. The fact that the phosphate ester salt is seen as round globules in the fiber cross section and in rod-like streaks in the fiber longitudinal section results from the drawing of the fiber after it has been spun.

DESCRIPTION OF PREFERRED EMBODIMENTS In a preferred embodiment of the present invention, the salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol is the sodium salt and the said monoalkyl group contains at least about carbon atoms. 'In a highly preferred embodiment of the invention, the salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol is a sodium salt of a lauryloxypoly(ethyleneoxy) acid phosphate of the formula wherein n is l or 2 and x is about 4.

Other additives may also be present in the improved acrylic fiber of the invention. In a highly preferred embodiment of the invention, the acrylic fiber contains parafiin wax together with the salt of a partial ester of phosphoric acid with a monoalkyl ether of a polyoxyalkylene glycol throughout the cross section of the fiber. Titanium dioxide may also be present as a delusterant. Additional additives, such as an optical brightener, may be present.

In a preferred process embodiment of the invention, parafiin wax and a sodium salt of a lauryloxypoly(ethyleneoxy) acid phosphate are dispersed in a solution of the acrylonitrile polymer in dimethyl formamide to form a homogeneous spinning solution, and the spinning solution is then extruded through orifices of a spinneret to form fibers. In a highly preferred embodiment, an aqueous emulsion of the paraffin wax and sodium salt of the lauryloxypoly(ethyleneoxy) acid phosphate are dispersed in the polymer solution.

The term acrylonitrile polymer, as used herein, refers to any long chain synthetic polymer composed of at least 85% by weight of acrylonitrile units of the formula,

in the polymer chain. As is well understood, the term includes both the homopolymer of acrylonitrile and copolymers of acrylonitrile and monoethylenically unsaturated monomers polymerizable with acrylonitrile. Nonlimitative examples of preferred comonomers include methyl acrylate, methyl methacrylate, vinyl acetate, styrene, methacrylamide, methacrylonitrile, vinyl chloride, vinylidene chloride, methyl vinyl ketone, 2- vinylpyridine, 4-vinylpyridine, Z-methyl-S-vinylpyridine, and sodium styrene sulfonate.

The term acrylic fiber, as used herein, refers to a fiber of acrylonitrile polymer, as defined above, which may contain additives such as the phosphate ester salt or other additives.

EXAMPLES Preferred embodiments of the invention will be illustrated by the examples that follow. Parts and percentages are by weight unless otherwise indicated.

Example I An N,N-dimethylformamide (DMF) solution containing 31% by weight total solids of the following materials is prepared:

(A) a terpolymer consisting essentially of 93.6% acrylonitrile, 6% methyl acrylate, and 0.4% sodium styrenesulfonate (B) 0.4% TiO' based on polymer weight, as a delusterant (C) 0.25%, based on polymer weight, of a mixture of 40% paraffin wax and 60% of the sodium salt of a mixture of monoand di-esters of phosphoric acid and an alcohol prepared by condensing lauryl alcohol with 4 mols of ethylene oxide. To facilitate addition of this mixture, 10% by weight of water is added to it to prepare an emulsion.

The solution is continuously dry-spun to a multifilamentary tow which, after simultaneous drawing 4.5 X and extracting in a water bath maintained near its boiling point, has a denier per filament of about 3. The tow is designated as Tow I. Examination of surface replicas of fiber cross sections and fiber longitudinal sections, using an electron microscope (Stereoscan electron microscope manufactured by the Cambridge Instrument Company), reveals the presence of the TiO and the phosphate ester salt in dispersed form.

As a control, a multifilamentary tow is prepared following the identical procedure, except that the parafiin wax/phosphate ester sodium salt of item (C) is omitted from the spinning solution. This tow is designated as Tow CI.

Tow I is converted to a sliver of staple fibers on a commercially available stretch-breaking machine of the type shown in US. Pat. 2,748,426 to W. K. Wyatt (manufactured by the Turbo Machine Company and designated as the Turbo Stapler) and processed to worsted count staple yarn in conventional manner on the worsted spinning system. As a control, Tow CI is stretch-broken to staple sliver and processed to staple yarn under iden tical conditions. The amount of waste collected at various stages of processing the tow and staple sliver to yarn is listed in Table I, together with the quality of the resulting yarns as measured by the yarn unevenness. The yarn unevenness as measured by the coefficient of variation is defined as the square root of the average of the squares of the deviation of linear density from the average linear density, expressed as a percentage of the average linear density within the tested length of strand. A higher number corresponds to a more uneven yarn.

TABLE I Tow C-I Tow I Turbo waste (grains/ lbs.) 56 Roving waste (grains/100 1bs.) 101 69 Splnnmg Waste (grains/100 lbs.) 208 88 Yarn fly Waste (percent) 0. 095 0. 052

Yarn unevenness, percent coeific nt of v 00 Example II (1) No additive is incorporated in a control identified as Tow C-II.

(2) 0.15%, based on polymer weight, of paraflin wax is incorporated as the sole additive in a second control 6 good fiber physical properties are retained even when high levels of the additive are employed.

What is claimed is: 1. Multifilament tow of textile fibers of acrylonitrile identified as Tow C-P. 5 polymer having dispersed throughout the cross section (3) 0.15%, based on polymer weight, of the sodium of the fibers a salt of a partial ester of phosphoric acid salt of a mixture of monoand di-esters of phosphoric with a monoalkyl ether of a polyoxyalkylene glycol; acid and an alcohol prepared by condensing lauryl alcosaid salt being present in the amount of about 0.05% hol with 4 mols of ethylene oxide is incorporated as the to about 3% by weight of the ploymer. additive in a tow designated as Tow II. 2. The fibers as in claim 1 wherein said salt is a (4) 0.15%, based on polymer Weight, of a mixture sodium salt of a lauryloxypoly(ethyleneoxy) acid phosof 40% paraflin wax and 60% of the sodium salt of a phate of the formula mixture of monoand di-esters of phosphoric acid and 0 an alcohol prepared by condensing lauryl alcohol with II 4 mols of ethylene oxide is incorporated as the additive [012E250(CH2CH2O)]P(ONa)3 in a tow designated as wherein n is 1 or 2 and x is about 4.

The results are listed in Table II. 3. The fiber as in claim 1 wherein said salt is in the As a further comparison 6 denier per filament tow in form of rod-like globules with the longitudinal axes which no additive is incorporated is prepared and a finish of the globules extending in the direction of the fiber comprising a mixture of 40% paratfin wax and 60% of length. the sodium salt of a mixture of monoand di-esters of 4. The fibers as in claim 1 having a denier within phosphoric acid and an alcohol prepared by condensing the range of about 1 to about 20. lauryl alcohol with 4 mols of ethylene oxide is applied 5. Fibers prepared from the tow of claim 1 in the to the tow in 20% aqueous emulsion in the amount of form of a staple yarn having a worsted count within 0.42%, based on the dry weight of the tow, after the tow 5 the range of 1/10 to about l/ 40. has been crimped. When this tow is stretch-broken to 6. The fibers as in claim 1 in which the polymer staple sliver and processed to staple yarn under the same comprises at least 85% acrylonitrile and up to 15% conditions employed with the tows of Table II, the total of a monoethylenically unsaturated monomer copolymwaste collected is 917 grains/ 100 lbs. and the yarn fiy erizable with acrylonitrile. waste (percent) is 0.1005. 7. The fibers as in claim 1 wherein a paraffin hydro- TABLE II Results from fibers of Control results the invention Tow C-II Tow C-P Tow II Tow II-P Turbo and rebreaker waste (grains/100 lbs.) 37 354 302 196 Pindrafer waste (3 drafts) (grains/100 lbs.) 252 216 183 153 Roving waste (grains/100 lbs.) 87 94 40 50 ra ri a a iii ir rii i i wiilcent fl '.I -II 0. 1367 o. 1165 0. 0649 o. 0604 Example III carbon having a chain length of at least a length corresponding to an oil is dispersed as an exterior through T0 illustrate the feasibility of Spinning filaments readout the cross section of the fiber along with said salt. y at high levels of the Phosphate ester Salt additive, a 8. The fibers as in claim 7 wherein said hydrocarbon spinning solution is prepared containing the following i i l il, materials: 9. The fibers as in claim 7 wherein said hydrocarbon (A) 5,000 g. of N,N-dimethylformamide, i paraffin 0 g. f a terpolymer consisting essentially of 10. In the production of synthetic fibers of acrylic 935% acrylonitrile, 6% methy acrylate, and 0.4% polymer in which the polymer is dissolved in a solvent dium styrenesulfonate, to provide a spinning soluiton and the resulting solution (C) 9.7 g. TiO as adelusterant, is extruded in a spinning Zone to form filaments which '(D) 1.62 g. of citric acid as a color inhibitor, are subsequently processed to produce acrylic fibers; the

(E) 35 g. of a pure, saturated, hydr c r n mineral improvement which comprises including in said spinning oil, and solution of salt of a partial ester of phosphoric acid 35 of the Sodium Salt of a Xt e f monowith a monoalkyl ether of a polyoxyalkylene glycol, and di-esters of phosphoric acid and an alcohol prepar said salt being present in said solution in the amount y condensing lauryl alcohol h 4 mols of ethylene of about 0.05 to about 3% by weight of the polymer oxide. to provide a dispersion of the salt throughout the cross In the above mixture the additive incorporated in ac- Section Of the fi s l cordance with the process of the present invention there- The Process as In Clalm 10 Whefelll Sa1d salt 15 fore comprises 3.0%, based on polymer weight, of a a Sodium Salt of a 'y yp y( y y) acid P mixture of 50% mineral oil and 50% of the phosphate Phate of the formula ester salt. The solution is continuously dry-spun to form H filaments and then simultaneously drawn 4.5x and extracted in a water bath maintained near its boiling point. [CuHzsOwHzoHzmxln P (ONMH The resulting filaments are readily processed to staple fibers and converted to staple yarn. The fibers have a wherein n is 1 or 2 and xis about denier per filament of 5.2, a tenacity of 2.31 g.p.d., an The process as in Claim 10 wherein the polymer elongatlon of 269% a modulus of and a comprises at least 85% acrylonitrile and up to 15% work-to-break of 0.41 g.p.d. Control filaments spun from of a monoethylenically unsaturated monomer copolym the Same ingredients listed above exceptmg that no erizable with acrylonitrile, and the solvent is N,N-dieral oil and no phosphate ester salt is added, have a denier th 1f id P filament 0f a tenacity 0f P- an 61011 13. The process as in claim 10 wherein a parafiin hygati f a modulus of -P- d a Workdrocarbon is included in said spinning solution as an to-break of 0.43 g.p.d. This experiment illustrates that extender along with said salt.

14. The process as in claim 11 wherein said salt and 3,180,845 4/1965 Knudsen et al. 26030.8 said paraffin hydrocarbon are added to the spinning 3,341,343 9/1967 Beiswanger et :11. 2528.6 solution as an aqueous emulsion. 3,434,874 3/1969 Proffitt 2528.6

3,475,364 10/1969 Trapasso 264176 References Cited 2,5s0,050 12/1951 Sparks et al. 260-28.5 GRIFFIN Asslstam Exammer 2,748,426 6/1956 Wyatt 19.37 2,784,169 3/1957 Slocombe 260-45.? 10 3,056,744 10/1962 Copes et a1. 2528.8 117139.5 CQ; 161174; 26028.5 -R, 30.6R, 33.6 3,113,369 12/1963 Barrett et al. 117139.5 UA, DIG. 23; 264176 F 2 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 618,()'Z Dated Inventor(s) Imrg M Mfr It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

column 6, Claim 1, line 6: "ploymer" should read --polymer--.

Column 6, claim 7, line 3: "exterior" should read --extender--.

Column 6, Claim 10, line 3: "soluiton" should read --aolution--.

Signed and sealed this 25th day of April 1972.

(SEAL) Attest:

EDWAED M.FLETCEER,JR. ROBERT GQTTSCHALK Attesting Officer Commissioner of Patents 

